Anode for mercury vapor rectifiers



Jan. 31, 1933. M sc 1,895,944

ANODE FOR MERCURY VAPOR RECTIFIERS Filed July 1, 1929 IINVENTOR Mari tz Schenkel.

BY I

ATTORNEY Patented Jan. 31 l33 UNITED STATES nomrz SGHENKEL, or BERLIN-CHARLOTTENBURG,GERMANY, assronon '10 wEs'rINe V V HOUSE ELECTRIC & MANUFACTURING COIVL IJA NY,.AG01RPOJRA'IiIOIV or rENnsYL VANIA ANODE FOR MERCURY VAPOR RECTIFIERS H Application filed July 1, 1929, Serial No. 375,005, and in Germany July 7, 1928. a i Y My invention relates to mercury arc rectifiers and more particularl to means for preventing the formation harmful deposits 7 that during the blocking period, that is, the

duration of predetermined, high voltage part.

' of the cycle and existing for about two-thirds of the cycle, the so-called cathode evaporation takes place in the neighborhood of the anodes, the products of which deposit principally upon the surface of the anode supporting insulators which serve to lead-in the anodes into the tank. Conducting deposits are thus formed on the insulators, which vary the field distribution near the anode, diminish the creepage paths and even cause occasional electric discharges which may be propagated to the anodes.

The cathode evaporation is further favored by the so-called residual charges, that is, charge-carriers which remain behind, from the current-flow period in which the electric- 7' ity-carriers of dilferent signs are segregated,

and thus the evaporation can be limited by neutralizing the charge-carriers remaining from the blocking period. The present invention is based on this principle. According thereto, metal surfaces are provided near the insulating surfaces which are to be protected from the befouling deposits, which metal surfaces are capable of neutralizing the residual charges which are present in this region. 7

In the drawing, the single figure is a sectional view through one of the anode shields of a metal-tank mercury-arc rectifier embodying my invention.

In the drawing, 1 denotes the anode of iron or of graphite, insulated from the rectifier tank by insulators 2 and 3, which are provided with channels and ribs to increase the creepage paths. The upper insulator 3 has a relatively wide petticoat 4 which'protects the anode against condensed mercury falling from the upper part of the tank. An anode-protecting tube or shield 6 is suspended on the insulat0r3 by a holder 5.

Since the products of the cathode evaporation, conveyed by the residual charges,jare 7 mainly deposited upon1the projecting ribs and in thegrooves of the insulators, these places are protected, according to the present invention, by keeping away the residual charge carriers which are still present during the blocking period. For this purposje, .a number of metallic surfaces, 7 7a, 8, 8wand 9, preferably in the form of grids, such as cylindrical rings or segments, are arranged in front of the insulators, and said surfaces rapidly neutralizethe charge-carriers in their vicinity. For the desired eifect,it is advantageous that at leastone of theneutralizing surfaces shall be disposed as close as possible to the anode but without being in directcontact therewith, in order that no residual charges may then be able to enter into the I space between the neutralizing surface and the anode. The neutralizing surface 9 inithe neighborhood of the anode is thus held, at such a, distance from the anode that this distance falls within the order of'magnitude ofthe dark space. I claimas my invention: 1. A mercury-arc rectifier: characterized by ananode an anode-insulator above the same and havmg a lower portion adj acentlt'o the lower endthereof, and a grid] structure disposed in spaced relation in vfront ofthe =1 lower portions of said insulator and in spaced relation over the joint between the same and the anode, the top of said grid structure terminating at some'considerable distance above s'aid'joint, and-the bottom of said grid strucf- 1.

ture terminating at some considerabledisstructure terminating at someconsiderable distance above said ,joint, andthe bottom of said grid structure terminating at some considerable distance belowsaid joint but above tance below said joint but above the extreme the extreme lower end of said anode, said grid structure extendingclose to, but not into contact with, either said lower end of the anode or saidlower portion of the anodeinsulator.

3. A mercury-arc rectifier characterized by an anode, an anode-insulator above the same and having a lower portion adjacent to the lower end thereof, and a conducting grid structurejdisposed in spaced relation in front of the lower portions of said insulator and in spaced relation over the joint between the same and the anode, the top of said grid structure terminating at, some considerable distance above said joint, and the bottom of said grid structure terminating. at some considerabledistance below said joint but above the extreme lower end of said anode, said grid structure extending close -to,b-ut not into contact with, either said lower'end of the anode or said lower portion of the anode-insulator,

the spacing being within theorder' of'magnitude of the dark space.

4. A mercury-arc rectifier characterized by an anode, an anode-insulator above the same and having a lower portion adjacent to the lower end thereof, and a plurality of spaced concentric metalrings surrounding, but not touching, the lower portion of said insulator and extending in spaced-relation across the joint between saidinsulator and the lower end of said anode, said metal rings being close to, but spaced from, the anode-insulator for some considerable distance above said joint between said insulator and said anode, the lowest portion oftheinnermost ring being at some considerable distance belowsaid joint but above the extreme lower end of the exposed anode-portion.

5. A mercury-arc rectifier characterized by fan anode, an anode-insulator above the same and having a lower portion adjacent to the lower end thereof, a tubular. anode-shield spaced fromthe exposed "lower endof the anode, and {extending above and below the 7 same, and a plurality of spaced concentric metal'ringssurrounding thelower portion of 'Said insulatorand extending acrossxthe joint 1 1 at jB erlin-Siemensstadt, Germany.

between said insulator and the lower end of said anode, said metal rings comprisingportions which are close together at every point between the lateral surface of the exposed anode-portion and the-top of the anodeshield,saidfm'etal rings being closecto 'but spaced from, the anode-insulator for some considerable distance above said joint between said insulator and said anode, the lowest portion of the innermost ring being at i some considerable distance below said joint but above the extreme lower end of the exposed anode-portion;

V In testimony whereof, have hereunto-sub- ,scrlbed my name this 17 th' day of June, 1929,

MORITZ SCHENKEL] 

